A successful clinical study of forty cancer patients showed that membranes from human melanoma cells infected with vesicular stomatitis virus and UV inactivated gave markedly more sensitive and a specific cancer skin test reaction that membranes from nonvirus infected cells. Mouse model for cancer immunotherapy with "virus augmented" tumor transplantation antigen. Cell membrane preparations from influenza virus infected squamous cell carcinoma and fibrosarcoma induced stronger tumor protection than membranes from noninfected tumor cells. Soluble, purified preparations showing "virus-augmented" activity were prepared. Spontaneous neoplastic transformation in vitro is a form of foreign body tumorigenesis. Freshly explanted Balb/c adult connected tissue cells were not tumorigenic when inoculated subcutaneously in fluid suspension, but were definitely tumorigenic after only 21 days in culture when inoculated attached to 1x5x10 mm plastic plates. New in vivo assay for tumor invasivity (and therefore malignancy). A technique for evaluating the invasion of inoculated tumor cells through the kidney capsule and into the kidney histo-architecture was developed and correlated with in vitro properties of density, anchorage, and serum growth regulation.